Is there gravity in space? Why astronauts float, explained
By the WhyCosmos team · Last updated:
Yes, there is gravity in space. Gravity is the pull between anything with mass, and it reaches across space, getting weaker with distance but never switching off. At the height of the International Space Station, Earth's gravity is still about 90 percent as strong as on the ground. Astronauts float because they and their station are falling around Earth together.
Ask a room of adults why astronauts float, and many will say there is no gravity in space. It is one of the most common misconceptions about space, and it gets the physics backwards: gravity is what keeps the space station in orbit in the first place. When Shubhanshu Shukla became the first Indian aboard the International Space Station in 2025, he floated for exactly the reason this page explains.
How to explain it to your child
Explain it to an 8-year-old
When you jump off a step, for a split second you feel light, because you are falling. Astronauts feel like that all the time. Their space station is falling towards Earth, but it is also zooming sideways so fast that it keeps missing the ground and falls around Earth instead. Gravity never switched off; they are simply falling together with their spaceship.
Explain it to a 13-year-old
Gravity weakens with distance, but 400 km up it is still about 90 percent of its strength at the surface. The ISS moves sideways at about 28,000 km per hour, so as it falls towards Earth, the curved surface drops away beneath it at the same rate. That continuous free fall is an orbit. Because the station and everything in it fall together, nothing presses on anything else, and astronauts experience microgravity: almost no apparent weight.
Key facts
| Is there gravity in space? | Yes, everywhere; it weakens with distance but never stops |
|---|---|
| Gravity at the ISS's height (about 400 km) | About 90 percent of the pull at Earth's surface |
| Why astronauts float | Continuous free fall around Earth, called microgravity |
| Speed of the ISS | About 28,000 km per hour, one orbit roughly every 90 minutes |
| Gravity on the Moon | About one-sixth of Earth's |
| Mass vs weight | Mass stays the same everywhere; weight changes with gravity |
| First Indian on the ISS | Shubhanshu Shukla, Axiom-4 mission, June to July 2025 |
| Effect on the body | Muscle and bone loss without daily exercise |
Why is there gravity in space?
Gravity is the attraction between objects that have mass. Earth has mass, so it pulls on everything around it; so does the Moon, the Sun, and even you, very slightly. The more mass an object has, the stronger its pull, and the farther away you are, the weaker it gets. But it never suddenly switches off when you leave Earth's atmosphere. Space has no air, but air has nothing to do with gravity.
Why do astronauts float if gravity is still there?
Because they are falling. Isaac Newton explained this with a thought experiment. Imagine a cannon on a very tall mountain firing a ball sideways. The ball curves down and lands some distance away. Fire it faster and it lands farther away. Fire it fast enough, and Earth's curved surface falls away beneath the ball as quickly as the ball falls, so it never lands at all: it keeps falling around Earth. That is an orbit.
A spacecraft in orbit is that cannonball. The station and the astronauts inside it are all falling around Earth together, at the same rate, so the astronauts do not press against the floor. Relative to their station, they float.
Is there really zero gravity in space?
Not in orbit. "Zero gravity" is a common phrase, but it is misleading, which is why NASA uses the word microgravity instead. Microgravity describes the condition in which people and objects seem almost weightless because they are in free fall. Small forces, such as the thin air drag on the station, mean it is never perfectly zero.
You do not even need to go to space to experience it. Aircraft that fly in steep up-and-down arcs give passengers around 20 seconds of weightlessness at a time, and space agencies use these flights to train astronauts and test experiments.
What is the difference between mass and weight?
Mass is the amount of matter in an object, measured in kilograms. Weight is the force of gravity pulling on that mass. Your mass is the same everywhere; your weight changes with gravity.
A child with a mass of 30 kg still has a mass of 30 kg on the Moon, but the Moon pulls only about one-sixth as hard as Earth, so a bathroom scale, which really measures force, would read about 5 kg. In the orbiting space station, a scale would read almost zero, which is why astronauts measure their mass with devices that use springs and Newton's laws of motion instead.
Does gravity work on the Sun, stars and galaxies?
Yes. Gravity shapes the whole universe. It pulls clouds of gas together to form stars, keeps planets in orbit around the Sun, holds hundreds of billions of stars together in a galaxy, and drives galaxies to collide and merge. At its most extreme, gravity crushes collapsing stars into neutron stars and black holes.
Even the Moon, about 384,000 km away on average, is held in orbit by Earth's gravity, and the Moon's own gravity pulls back on Earth's oceans to raise the tides.
What happens to the human body in microgravity?
Our bodies evolved under Earth's gravity. Without it, muscles weaken, bones lose density, fluids shift towards the head, and the sense of balance is confused. NASA reports that astronauts can lose about 1 to 1.5 percent of their bone mass per month in space without countermeasures, which is why crew members on the ISS exercise for about two hours every day.
Understanding these effects matters for India's own human spaceflight programme, Gaganyaan. Rakesh Sharma became the first Indian in space in 1984, and in June and July 2025 Group Captain Shubhanshu Shukla spent about 18 days aboard the ISS on the Axiom-4 mission, carrying out experiments designed by Indian researchers.
Newton's and Kepler's laws, the rules that predict every orbit on this page, are lesson 3 of Astronomy 201, the WhyCosmos course that follows Astronomy 101.
Questions parents and kids ask
Yes. Gravity exists throughout space. It becomes weaker with distance but does not suddenly disappear; at the height of the International Space Station it is still about 90 percent as strong as on the ground.
Astronauts float because they and their spacecraft are in continuous free fall around Earth. Everything falls together, so nothing presses on anything else.
Microgravity is the condition in which people and objects seem almost weightless because they are in free fall, as on an orbiting spacecraft. It is a more accurate term than zero gravity.
Yes. The Moon's surface gravity is about one-sixth of Earth's, which is why astronauts there could bounce along and carry heavy equipment more easily.
There is no sharp boundary. Earth's gravity becomes weaker and weaker with distance, but in principle it reaches out indefinitely.
Yes. Gravity does not need air or any other material to work. It acts across the empty space between the Sun and the planets.
Your child asks questions like this every week.WhyCosmos runs live online astronomy classes for ages 8–16, taught by real astrophysicists — where questions like these are the curriculum.
Related terms in this glossary
Sources and further reading
NASA: What is microgravity? · NASA: Space station facts and figures · NASA: Humans in space · ISRO: Gaganyaan